1. Field of Invention
This invention relates to game timers, specifically to chess clocks.
2. Prior Art
Game timers designed to limit the thinking time of contestants are used primarily in chess, where they are known as chess clocks. Mechanical chess clocks came into use in the late 1800's and were beginning to replace sandglasses by 1880. They were used exclusively in the London international chess tournament of 1883.
A chess clock actually comprises a pair of clocks running alternately. Each clock is controlled by a switch, usually in the form of a pushbutton. Once the device has been started, the pushbutton associated with the clock that is running stops that clock and starts the clock on the other side. After a player makes a move on the board, that player pushes the button on his/her side, which stops his/her clock and starts the opponent's clock. This action is said to complete the player's move. The opponent then begins consideration of the next move and pushes the button associated with his/her clock after the move is made. The cumulative time spent by each player over the course of the game is registered separately, counting down from time initially allotted on each clock. The players are required to complete a certain number of moves within the time initially allotted. Overstepping the time limit by either player results in forfeit of the game.
The occurrence of a time forfeit with a mechanical clock can be determined precisely by a small trip lever or flag, designed to fall just as the minute hand of the running clock reaches the top of the hour. In modem digital versions of the chess clock, which first appeared in the 1970's, overstepping the time limit is signaled by various alarm mechanisms, either audio or visual. Digital chess clocks, powered by an electrical source, are similar in operation to mechanical chess clocks from the standpoint of the user. An important advantage of the digital mechanism is that it makes possible variations on the traditional chess clock, such as the Fischer Clock described below. The term chess clock hereafter will imply a digital chess clock unless otherwise specified.
Time Controls and Playing Speed
The time limit to be enforced by a chess clock is known as a time control. A time control traditionally specifies a number of moves to be completed within a period of time, for example, forty move in two hours. If a game produces no result after the required number of moves, a secondary time control goes into effect. The secondary time control is typically different from the primary time control, perhaps twenty moves per hour (as compared with forty moves in two hours). Each player is credited with unused time from the previous time control. In the example chosen, one hour is added to the respective times upon completion of the initial forty moves on each side, and a sequence of twenty moves begins. A similar procedure, favored for its simplicity in digital clocks, is to allow the initial time to run its course, proceeding to the next time control only after the allotted time has been used up. If a player has then completed more than the required number of moves, he/she will have fewer moves to complete in the next time control. This variation in implementation depends on how the boundary between time controls is defined. If the time control is viewed as ending after the required number of moves, the time remaining is carried over the next time control. If the time control is viewed as ending after the prescribed period of time, the number of moves completed beyond the required number is carried over. By either procedure, the secondary time control may be followed, if necessary, by a tertiary time control with further variation on the basic time limit, or time controls may simply be repeated to the end of the game.
There is an important distinction to be made between the terms time control and playing speed. Playing speed refers to the number of moves completed in a standard unit of time, either minutes or hours. The traditional time control implies a specific playing speed. For example, a time control of forty moves in two hours implies a playing speed of twenty moves per hour. A given playing speed, on the other hand, may be implemented by any number of time controls. Thus, twenty moves per hour may be implemented by a time control of forty moves in two hours, twenty moves in one hour, ten moves in thirty minutes, and so forth.
Sudden-Death Time Controls
The end of a time control in serious competition is often the occasion to break off play for as much as a day or two. This poses a problem for the scheduling of tournaments. In recent years a radically different time control, known as sudden death, has become popular for amateur events. A sudden-death time control requires that all of the moves in a game be completed within a specified period of time allotted to each player. Thus, a time control of SD/60 means that each player must complete all of his/her moves within 60 minutes, and a game consequently cannot go longer than two hours. Sudden death often produces a time scramble for either or both players, where an indefinite number of moves must be completed within an ever-diminishing period of time. The pressure to avoid a time forfeit, besides taking its toll on the players, leads to low levels of chess that may descend into outright farce. Time scrambles are not uncommon under traditional time controls, though perhaps less severe. Under either type of time control, players tend to spend a great deal of time on their early moves, looking for a decisive advantage. If the advantage does not materialize, a time scramble may result.
The Fischer Clock
The problem of time scrambles was addressed by a 1988 invention of Robert J. Fischer (U.S. Pat. No. 4,884,255), called the Fischer Clock. In its main embodiment the Fischer Clock features a sudden-death time control that expands as moves are completed. The clock mechanism adds a predetermined amount of time, typically one or two minutes, to a player's remaining time for every move that he/she completes. The awarded increment, like the initial allotment of time, is essentially arbitrary. Fischer pointed out that: (1) if a player spends time equal to the increment on each move, he/she will always have the initially allotted time remaining on his/her clock; (2) if a player spends less time than the increment on any move, he/she will thereby add time on his/her clock for use on future moves; and (3) if a player spends more time than the increment on any move, he/she will use up either time stored up from previous moves or time from the initial time period. This scheme usually manages to avoid severe time scrambles. A disadvantage of the Fischer clock is that its time control bears no obvious relation to speed of play, on which traditional time controls are based (as, for example, forty moves in two hours). It may be for this reason that the Fischer Clock has not been widely adopted. Players using the clock have been known to complain that even the slowest of their opponents always seem to have a minute or two remaining.
Time Delays
Somewhat more popular as a means for combating time scrambles is a digital clock that provides a time delay on each move (U.S. Pat. No. 5,420,850 to Cameratta et al., 1995). With this device a player's clock does not begin to count down precisely when the opponent's clock is stopped. There is instead a small delay, typically five seconds, which amounts to free thinking time for the player on the move. A player will always have, at a minimum, the period of the time delay to complete his/her move This is essentially equivalent to awarding the free time as an increment after the player's move, as in the Fischer Clock. In contrast to the Fischer Clock, if a player does not use up all of the time delay in making a move, the unused time is not added to his/her clock. The fact that time is never added to time remaining, also that delays are typically quite small, makes this adaptation more or less compatible with traditional time controls.
Time delays over the course of a game tend, however, to distort the intended speed of play. Official rules of the United States Chess Federation (5th ed., 5F) provide that a tournament director has the right to deduct time from a time control in compensation for delay mode. The rule is applied mainly to sudden-death time controls, where the appropriate deduction is estimated from the number of moves required for a complete game. This estimate is necessarily crude since the actual number of moves required for a complete game varies widely. Another problem is that a player may not use up the entire period of the delay on any single move, particularly in time pressure. Consequently, the amount of additional free time accruing from a delay cannot be precisely determined.